HRD Detects Topaz Imitating Diamonds

RAPAPORT... HRD Antwerp has identified two stones that
were believed to be diamonds as topaz, reflecting a trend to fool rough diamond
buyers with the cheaper gemstone.

The two large, near-colorless rough
stones, weighing 50.08 carats and 38.18 carats, were submitted recently to HRD’s
research department to determine their quality, the diamond laboratory said
last week. Investigation of the growth lines of the
stones revealed them to be topaz, a silicate mineral of aluminium and fluorine,
rather than diamonds.

Topaz is a colorless diamond simulant,
with a similar density to a diamond, that can easily be misidentified. The market value of topaz, measured in US
dollars per carat, is far below that of rough diamonds.

Topaz and diamonds display very
different growth lines and growth structures due to their particular
crystallization. A Raman analysis, used to provide a
structural fingerprint by which molecules can be identified, clearly indicated
that the heavily included stones were topaz and not diamond. A detailed study of the large inclusions
also showed the presence of typical inclusions of topaz that are not generally found
in diamonds.

“It seems obvious that the topaz
crystals were manipulated and polished to show the typical growth lines and
growth structures of diamonds to fool any potential buyer,” HRD said.

“The value of this quality of colorless
topaz is believed to be not more than $5 per carat worldwide. More and more
topaz [stones] are cut to fool rough diamond buyers,” the laboratory added.

According to the Gemological Institute
of America (GIA), topaz is one of many near-colorless diamond simulant
materials that may be faceted to bear a closer resemblance to a diamond.